Citigroup rose 3 percent after the bank turned in better-than-expected results and disclosed it has agreed to pay $7 billion to settle a federal probe into its mortgage securities business. JPMorgan Chase & Co. and Goldman Sachs, due to report earnings today, also got a lift.

The Dow Jones Industrial Average gained 111.61 points, closing at 17,055.42, the index' first close above the 17,000 mark since July 7.

All told, the three major stock indexes notched their second gain in two days. That's a turnaround from last week, when the Standard & Poor's 500 index lost 0.9 percent, its worst showing since April.

The gains come as news service Bloomberg reported that individual investors are plowing money back into the U.S. stock market just as professional strategists say gains for this year are over. About $100 billion has been added to equity mutual funds and exchange-traded funds in the past year, 10 times more than the previous 12 months, according to data compiled by Bloomberg and the Investment Company Institute.

The growing optimism contrasts with forecasters from UBS AG to HSBC Holdings, who say the stock market will be stagnant with valuations at a four-year high. While the strategists have a mixed record of being right, history shows the bull market has already lasted longer than average and individuals tend to pile in at the end of the rally.